The objective of the proposed research is to study the mechanisms of transduction in freestanding lateral line organs in the semicircular canals. We propose to investigate the dynamic relations between cupula motion, displacement of hair-cell cilia, membrane conductance changes, receptor potentials, extracellular microphonic responses, synaptic activation and nerve activity. In lateral-line organs, microelectrode techniques will be used to record from hair-cells, supporting cells, and nerve fibers. We will attempt to measure ion specific conductance changes using bridge circuitry or by automated voltage clamp methods. The possibility of producing synaptic activation in the absence of mechanical stimulation will be explored by directly controlling membrane potential. In the skate semicircular-canal, we have developed methods for introducing pipettes and electrodes into the ampulla without disturbing sensitivity. Using these methods, we propose to investigate the detailed mode of motion and attachment of the cupula. The role in transduction of specific ions in endolymph will be investigated by measuring effects of ionic changes on conductance across the crista and on afferent response. We will attempt to measure changes in endolymph composition before and after caloric stimulation, by electron probe microanalysis. Effects of ionic changes on afferent and efferent synapses and aspects of their pharmacology will be investigated. We anticipate that information regarding transduction mechanisms obtained from the study of these relatively simple and accessible organs will aid in understanding these processes in the phylogenetically related human vestibular and auditory organs.